Extendible and contractable pit props



July 12, 1966 L. w. TAYLOR EXTENDIBLE AND CONTRACTABLE PIT PROPS 6 Sheets-Sheet 1 Filed Aug. 4, 1964 July 12, 1966 w. TAYLOR 3,260,492

EXTENDIBLE AND CONTRACTABLE PIT PROPS Filed Aug. 4, 1964 6 Sheets-Sheet 2 July 12, 1966 L. w. TAYLOR 3,260,492

EXTENDIBLE AND CONTRACTABLE PIT PROPS Filed Aug. 4, 1964 6 Sheets-Sheet 3 July 12, 1966 1.. w. TAYLOR 3,260,492

EXTENDIBLE AND CONTRACTABLE PIT PROPS Filed Aug. 4, 1964 e Sheets$heet 4 July 12, 1966 w. TAYLOR EXTENDIBLE AND CONTRACTABLE PIT PROPS 6 Sheets-Sheet 5 Filed Aug. 4, 1964 "Ill FIG.6.

United States Patent 3 260 492 EXTENDIBLE AND doNTRAcTABLE PIT PROPS Laurence William Taylor, Woodthorpe, Nottingham, England, assignor to W. E. & F. Dobson Limited Filed Aug. 4, 1964, Ser. No. 387,355 Claims priority, application Great Britain, Aug. 10, 1963, 31,672/63 6 Claims. (Cl. 248-354) This invention is for improvements in or relating to extendible and contractable pit props primarily for use in mines where blasting occurs.

In these mines the pit props are particularly prone to damage by the blasting and the damage may be such that when the prop is operated to release for contraction in the usual manner by gravity, and particularly if the head is spiked, there is a tendency for the prop to remain fully extended.

An object of the invention is to provide a prop with special means to effect its contraction particularly when it is damaged by blasting.

The invention provides actuator means for contracting an extendible and contractable pit prop positively and adapted for one component of the actuator to be secured to the upper com-ponent of the prop and for the other component of the actuator to engage the roof, and means for operating the actuator to extend and press the props upper component downwardly using the roof as an abutment. Conveniently where the prop is of the type having a release valve operable by turning of an exposed end of a crank axle, the actuator is adapted for attachment by a pivoted arm to said boss so that release of the release valve is effected by the initial operation of the actuator. Conveniently also the actuator is adapted for removable attachment to the prop. The actuator, being situated externally of the prop, may have a lateral extension to a prop-engaging location substantially over the pivotal connection between the pivoted arm and the actuator.

An embodiment of the invention will now be described in greater detail by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a side view partly in diagrammatic section of an actuator device according to the invention;

FIGURE 2 is a plan view of the device;

FIGURE 3 is a side view of the device fitted to a pit P P;

FIGURE 4 is a similar view of FIGURE 3 showing the device partly operated;

FIGURE 5 is a similar view to FIGURE 4 showing the device fully operated;

FIGURE 6 is a side view of a modified actuator device according to the invention;

FIGURE 7 is a sectional view of a hydraulic pit prop with which the actuator device can be used.

Referring to FIGURE 1, there is provided an actuator device 1, for positive release of a hydraulic pit prop, in the form of a double acting piston 2 in a cylinder 3, with inlet and outlet ports 4, 5 for hydraulic or other fluid to obtain extension and contraction of the piston 2 which conveniently has a spiked outer end as at 6.

In addition at that side of the cylinder 3 opposite the ports 4, 5 there is a U bracket for a pivot bolt 8 on which there is pivotally mounted a lever arm 9 from which there projects a spigot 10 having a lead-in 11.

In use of the device it is applied to a hydraulic or other extendible and c-ontractible pit prop 12, FIGURE 3, having a projecting end 13 of a crank shaft which has a trans verse hole 14 usually to receive a crank handle for turning the crank shaft to release an internally mounted release valve for contraction of the prop.

Instead of using the ususal crank handle, the spigot 10 of the actuator device is engaged in the transverse hole 14 of the crank shaft 13, with the lever arm 9 in such a position that an inclined face 9a of it abuts the side of the cylinder 3 as shown in FIGURE 3.

When it is required to release the prop the actuator device is operated to extend the piston 2 so that the spiked end 6 engages the roof as in FIGURE 4 and thereafter the cylinder 3 rides down the piston 2 and in so doing causes the lever arm 9 to turn about the pivot 8 so as to also turn the spigot which consequently turns the crank shaft 13 and opens the release valve.

Further operation of the actuator device results in further lowering of the cylinder 3 on the piston 2 whereby the lever 9 is carried bodily downwards as in FIGURE 5 thereby to positively contract the prop 12 away from the roof.

It will be realised that the use of the actuator device is particularly advantageous in instances such as Where there is blasting in the mine which may have caused such damage to the prop that it would not automatically contract upon release of the release valve, whereas the provision of the actuator device first releases the valve and then ensures that the prop contracts by the device positively pushing the prop downwardly away from the roof.

In the modified form of actuator device, FIGURE 6, the outer end of the piston 2 is not spiked but instead has secured on ita cross bar 15 to the outer end of which there is secured a guide rod 16 mounted in a runway 17 and the inner end of which is spiked as at 18 at a location directly over the pivot 8 of the lever arm 9.

The advantage of this modificaiton is that the pressure exerted by operation of the device is transmitted from the piston 2 by the cross bar 15 to the spiked end 18 so that the pressure is applied to the roof at a location directly over the pivoted connection between the device and the lever arm 9.

FIGURE 7 shows further details of the hydraulic prop 12 with which the actuator device can be used. The crank shaft 13 is connected by a crank 15 to a piston rod 16 of a pump 17 by which hydraulic fluid is pumped from the upper hollow ram reservoir 18 into the lower pressure cylinder 19 for extending the prop.

For contracting the prop there is a release valve 20 which is connected by a link 21 to a lug 22 projecting from the pump rod 16. The link 21 has a slot 21a permitting oscillation of the crank shaft 13 by an externally fitted handle for operating the pump without affecting the release valve.

When it is required to operate the release valve to release the prop, an extended rotational movement of the crank shaft 13 is required and this is accomplished by the actuator device as hereinbefore described.

What I claim is:

1. In combination with an extendible and contractable roof-supporting hydraulic prop, and actuator device for positive release of said prop to disengage the upper component thereof from a roof, said prop having a projecting bush thereon for rotation to open a release valve in said prop to release hydraulic fluid under pressure, said actuator device comprising a double-acting piston and cylinder with inlet and outlet ports for hydraulic fluid and having a bracket for a pivotal bolt on which there is mounted a lever arm having a chamfered underface and from which there projects a spigot inserted in said projecting bush, the chamfer of the lever arm abutting the side of the prop.

2. The structure of claim 1, said double-acting piston having secured on the upper end thereof a crossbar to the outer end of which there is secured a guide rod mounted in a runway and the inner end of which is spiked at a rotation directly over the pivot of the lever arm.

3. The structure of claim 1, the upper end of said double-acting piston having secured to it a crossbar to the outer end of which there is secured a guide rod mounted in a runway and the inner end of which is spiked at a location directly over the' pivot of the lever arm, and having means whereby pressure exerted by the device is transmitted from the piston to be applied to the roof at a location directly over the pivoted connections between the device and lever arm.

4. An actuator device for use in positively releasing an extendible and contractable roof-supporting hydraulic prop, com-prising a double-acting piston and cylinder with inlet and outlet ports for hydraulic fluid. and having a bracket for a pivotal bolt on which there is mounted a lever arm having a chamfered underface and from which there projects a spigot.

'5. An actuator device according to claim 4 wherein the upper end of said double-acting piston has secured to it a crossbar to the outer end of which there is secured a guide rod mounted in a runway and the inner end of 4 which is spiked at a location directly over the pivot of the lever arm.

6. An actuator device according to claim 4 wherein the upper end of said double-acting piston has secured to it a crossbar to the outer end of which there is secured a guide rod mounted in a runway and the inner end. of which is spiked at a location directly over the pivot of the lever arm, and having means whereby pressure exerted by the device is transmitted from the piston to be applied to a roof at a location directly over the pivoted connection between the device and lever arm.

References Cited by the Examiner UNITED STATES PATENTS 2,461,810 2/1949 Curtis 248-354 CLAUDE A. LE ROY, Primary Examiner. 

1. IN COMBINATION WITH AN EXTENDIBLE AND CONTRACTABLE ROOF-SUPPORTING HYDRAULIC PROP, AND ACTUATOR DEVICE FOR POSITIVE RELEASE OF SAID PROP TO DISENGAGE THE UPPER COMPONENT THEREOF FROM A ROOF, SAID PROP HAVING A PROJECTING BUSH THEREON FOR ROTATION TO OPEN A RELEASE VALVE IN SAID PROP TO RELEASE HYDRAULIC FLUID UNDER PRESSURE, SAID ACTUATOR DEVICE COMPRISING A DOUBLE-ACTING PISTON AND CYLINDER WITH INLET AND OUTLET PORTS FOR HYDRAULIC FLUID AND HAVING A BRACKET FOR A PIVOTAL BOLT ON WHICH THERE IS MOUNTED A LEVER ARM HAVING A CHAMFERED UNDERFACE AND FROM WHICH THERE PROJECTS A SPIGOT INSERTED IN SAID PROJECTING BUSH, THE CHAMFER OF THE LEVER ARM ABUTTING THE SIDE OF THE PROP. 